Matter: Occupies space, has a mass, exists in 3 physical states namely solids, liquids & gases; composed of particles.
Solid: have fixed shape, fixed volume.
Liquid: takes shape of part of container below liquid level. No fixed shape, has fixed volume, flow easily.
Gas: when collected into vessels occupies all space inside vessel, takes shape of container, no fixed shape or volume.
Arrangement of particles in solids, liquids & gases
• Attractive force among particles strongest in solid. Particles are close together& arranged in a fixed pattern.
• Weaker attractive force in liquids than solids. Particles not as close as in solid but more closer than in gas. Particles loosely packed , have freedom of moving.
• In gases particles aren’t closely packed or orderly arranged. Attractive force in particles very weak. Can move freely & randomly at different speeds.
• Because interparticle distances in gas particles are very high , it can be compressed easily.
• When in a container, moving gas molecules collide with wall of container thus exerting pressure on the wall in every direction. When rate of collision molecules on wall increases, pressure exerted by gas increases. When collisions decrease, pressure exerted decreases.
• Factors affecting behavior of gas: temperature, pressure, volume, amount of substance.
Behaviour of gas when 2 factors are changed at a time keeping others constant
Variation of temperature Vs Pressure of fixed amount of gas of constant Volume ACTIVITY:
Heat the test tube with Bunsen burner keeping the stopper away from the body. Stopper will be thrown out from test tube due to increase of pressure inside. Thus, pressure of gas increases when temperature is increased.
• When temperature of gas is increased, speed of gas molecules is increased. Thus, no. of collisions of gas molecules per unit time per unit area is increased. Thus, pressure too